Prior art personal computer systems typically use microprocessors. When a microprocessor is used in a computer system, a socket is typically employed to secure the microprocessor onto the PCB on which other circuitry of the computer system resides. The socket is typically surface mounted or pin plugged onto the PCB. The socket also typically includes female type contact holes on the top of the socket for allowing pins of the microprocessor to be inserted so as to secure the microprocessor in the socket. FIG. 1 illustrates a prior art computer system 10 that employs a socket 11 to mount a microprocessor 12 on PCB 13. As can be seen in FIG. 1, socket 11 is mounted on PCB 13 on which other integrated circuits 14a-14n are mounted. Socket 11 can be surface mounted or pin plugged onto PCB 13. Microprocessor 12 is then inserted onto socket 11. Socket 11 may be a zero insertion force ("ZIF") socket which allows for zero insertion force insertion and removal of the microprocessor.
Computer system 10 can be upgraded in performance through substitution of elements. The new elements typically have higher performance capabilities than the elements already in the system. For example, computer system 10 of FIG. 1 can be upgraded by substituting microprocessor 11 with a new microprocessor of higher performance.
Disadvantages are, however, associated with the prior art computer system. One disadvantage is that it is typically difficult to upgrade a computer system by substituting the microprocessor in the original computer system with a higher performance microprocessor. This is due to the fact that each type of microprocessor typically has its own pin configuration and definition. A socket for an older generation microprocessor may not fit for a new generation microprocessor. In this case, a new socket is typically required. An example of this is a socket for an INTEL Pentium.TM. overdrive microprocessor, which typically contains an extra row of pin-sockets to accommodate the Pentium.TM. overdrive microprocessor than the socket for an INTEL i486.TM. microprocessor.
Moreover, each type of microprocessor typically requires different system configuration of the computer system. In addition, in order to accommodate a new upgrade microprocessor which is based on an alternate architecture, the microprocessor bus interface design for the original microprocessor must be drastically altered in order to allow the new upgrade microprocessor to function properly in the system that was designed for the original microprocessor. For example, the INTEL Pentium.TM. overdrive upgrade microprocessor is based on the Pentium.TM. microprocessor architecture. In order for the Pentium.TM. overdrive upgrade microprocessor to function properly in a system that was originally designed for INTEL i486.TM. microprocessor, the Pentium.TM. overdrive upgrade microprocessor's bus interface design must be changed to function as though it were operating on an INTEL i486 microprocessor bus. Thus, when an upgrade microprocessor is used to substitute the original microprocessor already in the system, additional logic circuits are typically required to interface the upgrade microprocessor with the circuitry of the computer system.
One prior solution to the problems is shown in FIG. 2. As can be seen in FIG. 2, a prior computer system 20 includes two sockets 21a and 21b mounted on a PCB 23. Socket 21a is used to secure an original microprocessor 22a on PCB 23 and socket 21b is used for an upgrade microprocessor 22b. An interface circuit 24n is mounted on PCB 23 to interface the microprocessors to other circuits of computer system 20. Typically, computer system 20 first operates with microprocessor 22a in socket 21a. When upgrade of the computer system 20 is needed, microprocessor 22a is either removed from socket 21a or electrically disconnected from the system. Upgrade microprocessor 22b is then plugged in socket 21b and computer system 20 operates with upgrade microprocessor 22b.
Disadvantages are, however, still associated with the prior arrangement as shown in FIG. 2. One disadvantage is that the printed circuit board is typically required to be relatively large in order to accommodate the two sockets. This typically causes the size of the computer system to be accordingly large. Another disadvantage is that the cost of the computer system typically increases as it contains more than one microprocessor socket in the system. At least one of the sockets is typically not used in the system at one time. Moreover, the printed circuit board also needs to house the interface circuit (i.e., interface circuit 24n of FIG. 2) that interfaces the microprocessors with the remaining circuits of the computer system. This typically occupies some space on the printed circuit board that causes the printed circuit board to be relatively large.